This invention relates to a pressure transmitter, and more particularly, to a fluid pressure transmitter assembly.
Present pressure sensor packages include a pressure sensor element (i.e., a silicon die having piezo resistive properties utilized to detect variations in pressure) mounted on a "PYREX" glass mounting tube which is included in a steel housing having a header, pressure feed-throughs,... and attached to a meter body.
The silicon die (pressure sensor element) has a relatively low thermal coefficient of expansion (TCE), and steel has a relatively high TCE. If the silicon die were mounted directly on the steel housing, temperature changes would induce strains on the silicon die which would result in erroneous pressure readings. Therefore, an intermediate material is used to mount the silicon die. As mentioned above, a commonly used material is "PYREX" glass, the glass having a TCE which more closely matches the TCE of silicon, and a common method of joining the silicon die to the "PYREX" glass is via a thermal-electric bonding technique.
The present invention mounts the silicon die without the use of an intermediate material; it uses a unique variation of a ceramic dual-in-line package, DIP, such as that used for the mounting of integrated circuit chips. The resulting simplicity of the pressure sensor assembly of the present invention yields features which include the ability to be mounted on a printed circuit board, a variety of mounting arrangements, ease and flexibility of mounting, and lower overall cost. Further, because the silicon die is mounted in a ceramic DIP package, the particular ceramic having a TCE approximately equal to that of silicon, the inducement of any false strains in the silicon die with temperature changes is essentially eliminated.